Re: [PATCH v1 3/5] vhost-user-blk: make it possible to disable write-zeroes/discard

[Stefan Hajnoczi]

On Wed, Aug 24, 2022 at 11:24:55PM +0300, Daniil Tatianin wrote:
> On 8/24/22 9:00 PM, Stefan Hajnoczi wrote:
> > On Wed, Aug 24, 2022 at 12:18:35PM +0300, Daniil Tatianin wrote:
> > > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> > > index 9117222456..e89164c358 100644
> > > --- a/hw/block/vhost-user-blk.c
> > > +++ b/hw/block/vhost-user-blk.c
> > > @@ -251,6 +251,8 @@ static uint64_t 
> > > vhost_user_blk_get_features(VirtIODevice *vdev,
> > >   {
> > >       VHostUserBlk *s = VHOST_USER_BLK(vdev);
> > > +    features |= s->host_features;
> > 
> > I think you can eliminate this if you use vdev->host_features in the
> > qdev properties instead of adding a separate s->host_features field.
> > That will simplify the code.
> Indeed, thanks for spotting that. I wonder why every virtio device
> implementation I've looked at has chosen to add their own host_features
> field (net/blk)?

It's for historical reasons. Over time more common behavior moves into
the core, but not all devices have been refactored to take advantage of
that.

Thanks,
Stefan

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